The government has refused an invitation to attend a public debate on the cost of new nuclear power today, which will be attended by industry figures, academics and many other interested parties.

Paul Dorfman, a senior research associate at Warwick University and the event's organiser, said it showed ministers were scared about the cost to consumers and taxpayers of nuclear power.

Companies at the forefront of plans to build new reactors, such as EDF and Centrica, have said they will attend the meeting at Portcullis House, next to the Houses of Parliament. But the Office for Nuclear Development (OND) – an arm of the Department of Energy and Climate Change – said: "On this occasion ministers and officials have decided not to attend."

Dorfman said the OND had offered to talk through the issues but insisted this happened in private. "The government do not want to be challenged in public. I think it is reasonable to assume that they are deeply concerned about their position and know reactors cannot be built at a competitive cost without public subsidies."

Based on the industry's track record, there is good reason to be sceptical about the economics of nuclear power, even before the debacle in Finland. The last reactor constructed in Britain was Sizewell B in Suffolk. It was originally budgeted to cost about £1.9bn but eventually came in at about £3bn. The cash was all provided by the public sector – half of it being taken from the nuclear levy that was created to help cover decommissioning and waste disposal costs.

There have also been financial – and technical problems – with other plants such as the mixed oxide (Mox) and Thorp fuel reprocessing facilities at Sellafield, the UK's largest atomic complex. Mox was meant to cost £265m but ended up costing £490m within three years. It produced only 5.2 tonnes of reprocessed fuel between 2001 and 2007, despite an promised annual output of 120 tonnes.

The government has also promised nuclear developers that taxpayers will meet any of their cost overruns from decommissioning the new reactors and storing the waste. Officials are in charge of setting a fixed price for the waste and experts are setting it deliberately high to factor in any cost overrun.

But Gordon MacKerron, who up to 2007 was chairman of the Committee on Radioactive Waste Management, set up by the government to work out how to deal with the UK's nuclear waste, admits that it will be decades before we know for sure what the bill is and whether the taxpayer will have to pay more.